ABSTRACT PI - Dennis E. Ohman, Ph.D. Title: Pathogenic Mechanism for Lung Infection in Mucoid Pseudomonas Many VA patients are susceptible and succumb to infections with the opportunistic pathogen, Pseudomonas aeruginosa. This can occur as a complication of emphysema, chronic bronchitis, cancer and immunosuppressive drug therapy. Exposure to this ubiquitous bacterium can result in nosocomial infections, which is common via respiratory ventilators, catheters, lumbar punctures and general surgery. P. aeruginosa is highly tolerant or resistant to most antibiotics, making it difficult to control such infections, which leads to a high mortality rate. The goal of this research is to improve our understanding of the biosynthesis of a protective capsule-like polysaccharide called alginate, which is produced as a virulence factor by P. aeruginosa. During chronic respiratory infections (e.g., COPD), adaptive mutations in vivo can lead to the over production of this exopolysaccharide such that clinical isolates demonstrate a mucoid colony morphology. Improving our understanding of this pathogenic mechanism in P. aeruginosa will enhance the management of pulmonary disease caused by this bacterium. Most of the enzymes for the production of alginate are clustered in an operon of 12 genes. In this study, we will: (1) evaluate the enzyme reactions in the formation of the main precursor of alginate, GDP-Mannuronate, (2) characterize the mechanism of alginate polymerization and cytoplasmic membrane transfer, (3) characterize the mechanism of alginate acetylation, which confers anti-phagocytic and thick biofilm properties, and (4) in collaboration with a structural biologist, determine the structures of alginate biosynthetic proteins to better understand the polymerization-secretion complex. The long-term goal of this research is to understand the functions of all of the components required for the biosynthesis of alginate, which is now recognized as a critical virulence factor during pulmonary infection. The information gained could be vital for the development of new therapeutic approaches in the treatment of P. aeruginosa infections. The results of these studies will also contribute to our overall understanding of bacterial capsule biosynthesis, which is a common mechanism of bacterial virulence for avoiding the host immune response. PUBLIC HEALTH RELEVANCE: Relevance PI - Dennis E. Ohman, Ph.D. Title: Pathogenic Mechanism for Lung Infection in Mucoid Pseudomonas Infection with the bacterium Pseudomonas aeruginosa is a significant problem among our veterans. Many VAMC patients are susceptible to opportunistic infections with P. aeruginosa due to complications with emphysema, chronic bronchitis, COPD and other disorders. Nosocomial infection during treatment with respiratory ventilators is also common. A key virulence factor of P. aeruginosa during pulmonary infection is the production of a capsule-like exopolysaccharide called alginate. A better understanding of the complex mechanisms involved in alginate biosynthesis could lead to novel therapies. This work is also of importance to the VA health system because Pseudomonas infections are very difficult to treat due to its innate antibiotic resistance.